Open GA-Ensemble and navigate to API DOCUMENTATION -> javafx -> stage -> Stage
In the docs, there are several images displaying stages.

If you right-click one of the images and click "Open in new window," it throws:
 
java.lang.NullPointerException
at ensemble.pages.DocPage$DocPane$1.invalidated(DocPage.java:159)
at com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:137)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:61)
at javafx.beans.property.ReadOnlyObjectWrapper$ReadOnlyPropertyImpl.fireValueChangedEvent(ReadOnlyObjectWrapper.java:151)
at javafx.beans.property.ReadOnlyObjectWrapper.fireValueChangedEvent(ReadOnlyObjectWrapper.java:117)
at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:86)
at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:119)
at javafx.scene.web.WebEngine.updateDocument(WebEngine.java:113)
at javafx.scene.web.WebEngine.access$700(WebEngine.java:57)
at javafx.scene.web.WebEngine$LoadWorker.dispatchLoadEvent(WebEngine.java:718)
at com.sun.webpane.platform.WebPage.fireLoadEvent(WebPage.java:2200)
at com.sun.webpane.platform.WebPage.fwkFireLoadEvent(WebPage.java:2031)
at com.sun.webpane.webkit.network.URLProcessor.endOfDataCallback(Native Method)
at com.sun.webpane.webkit.network.URLProcessor.access$300(URLProcessor.java:16)
at com.sun.webpane.webkit.network.URLProcessor$3.run(URLProcessor.java:86)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:29)
at com.sun.glass.ui.win.WinApplication$2$1.run(WinApplication.java:62)
at java.lang.Thread.run(Thread.java:662)